1. Field
The present teachings relate to amplifier biasing. In particular, the present teachings relate to biasing methods and devices for use in implementing power amplifiers.
2. Description of Related Art
Highly efficient microwave and RF amplifiers producing large output voltages (e.g., 14 to 16 V) are adopted for many applications. In order to be able to handle such large voltages during operation, a CMOS type power amplifier often presents devices arranged in a cascode configuration where the devices are stacked in series. The gates of the power amplifier devices used in the stack have bias voltages that are higher than the battery supply voltage. Such high voltages are usually not available in present technologies and they are provided separately.
A solution to this problem is to use charge pumps. However, using charge pumps to generate bias voltages may result in interference at charge pump frequency. Also, this solution involves design of more complex circuits. Moreover, using charge pumps increases the overall power consumption resulting in a lower power amplifier efficiency. See, for example, Charge Pumps Shine in Portable Designs, Maxim, Application Note 669 (Mar. 15, 2001), incorporated herein by reference in its entirety.